but all these could be used by a government to influence the voter behaviour such that they stay in power forever, China style.
you are ready for communism.
You're clearly convinced that governments slide inevitably towards authoritarianism and can only be prevented from doing so by practically restricting their powers, but it's a rather backwards way of thinking about things. An authoritarian government takes whatever powers it wants and wipes its arse with any rules that have been written to supposedly prevent it. If an authoritarian government thinks a CBDC will be useful it can just make one. Not that it would have to, because the government's existing powers are already sufficient to implement all the nefarious schemes people are worrying about in this thread.
The way to avoid the threat of an authoritarian government is to have a fair and well run electoral system, a healthy national political dialogue and a well educated population (not that these things are easy), not to assume the government is inevitably going to go bad and block it from implementing useful policies in a futile attempt to curtail the powers of the dictatorship you've convinced yourself it will one day become.
The solution to that logic is to abolish everything.